Hi They do seem to like the heavier pellets. I have been using the eun jin and the H&N baracuda with good results. I have tried the gamo PBA and they seem ok but not as accurate This is my first pcp and I am glad I picked the sumatra . Now I want another one so I guess I am hooked on pcp air rifles Are you using a pump or a tank? I m pumping takes a bit but fills it,